Types Of Furnace Ignitors: An In-Depth Guide

We understand how frustrating it can be to return home during the chilly winter months and find the room temperature too cold. A furnace is crucial to keeping your home warm and comfortable, particularly during colder seasons. The ignitor is responsible for starting the heating process by lighting the burner. 

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Ignitor issues can occur due to loose or damaged wiring. Regular maintenance is essential to avoid such problems.


Furnace ignitors are essential components that play a vital role in heating systems, and homeowners should pay attention to these tiny yet critical parts. This article will discuss the main types of furnace ignitors, the signs of malfunctioning furnace ignitors, and strategies for repairing gas furnaces.

The furnace ignitor is a crucial heating system component that significantly initiates ignition. When the thermostat signals the furnace to produce heat, the furnace ignitor creates the necessary spark or heat to ignite the fuel.

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The ignitor is typically silicon carbide or another durable material that can withstand high heat. It receives an electrical current from the control board, which causes it to heat up and start the ignition process. Proper functioning of the furnace ignitor is essential for optimal heating system performance.

Here is the list of different types of furnace ignitors:

If your furnace was manufactured within the last 20 years, it is likely equipped with a hot surface ignition (HSI) system. Compared to older pilot light ignition systems, this system reduces fuel waste by only burning fuel when the furnace runs, making it more energy-efficient. You can also learn more about types of HVAC filters.

Additionally, it operates more quietly than pilot light or direct spark systems, which make a loud clicking sound when they light up.HSI ignites gas using an electrically heated metal filament controlled by a thermostat. The HSI glows red-hot and ignites the gas when the thermostat signals the ignitor.

If your furnace was manufactured in the late 1980s through the 1990s, it may have a direct spark ignition system. This system is also commonly found in modern furnaces made by brands like Ruud or Rheem. Homeowners prefer this system as it has a longer lifespan.

This furnace system uses a high-voltage spark controlled by a thermostat to ignite gas. The thermostat sends an electric current to the ignitor, creating a spark that ignites the gas. Moisture and dirt can weaken or prevent this spark.

The intermittent pilot ignition system was widely used in furnaces from the 1950s until the late 1990s. It uses an automatic spark igniter to light the main burners through a gas pilot light that remains on continuously. The intermittent pilot ignition system uses a gas pilot light and an automatic spark igniter to light the main burners when heat is needed. 

The system is controlled by a thermostat that activates an electronic valve to release gas to the pilot burner. Once the pilot burner is ignited, the pilot flame stays on until the furnace is turned off. Although the intermittent pilot ignition system is energy-efficient and safe, it can clog and fail if the pilot burner or the gas valve is dirty or faulty.

The standing pilot light was an early furnace ignition system from the 1920s to the 1980s. An older furnace ignitor uses a continuous pilot flame to ignite the gas. Unlike modern furnaces that are controlled by a thermostat, the standing pilot light is controlled by a thermocouple. The thermocouple senses the temperature of the pilot flame and keeps the gas valve open as long as the pilot flame is on. When the furnace needs to start, the gas valve opens further, allowing more gas to flow to the main burner, which is then ignited by the pilot flame. 

Although the standing pilot light is simple and reliable, it wastes gas and energy by always keeping the pilot flame on.

The silicon carbide ignitor (SCI) ignites gas in a furnace. It has higher resistance and withstands higher temperatures than the hot surface ignitor (HSI). When the furnace starts, the thermostat sends an electric current to the SCI. It heats rapidly and ignites the gas. Although durable and efficient, the SCI is expensive and fragile. However, it’s much safer and more reliable than older types like SPI or IPI, as it doesn’t waste gas or pose a risk of gas buildup, and it’s easier to maintain and operate. Operate. 

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The SCI, a type of SiC device, is used in electronics and sensors and can operate at high temperatures or voltages. It’s used for LEDs, detectors, transistors, and integrated circuits, providing efficiency, durability, and performance advantages.

A malfunctioning furnace ignitor can cause the furnace to stop producing heat. Different types of furnace ignitors have various issues. Some common signs of a faulty ignitor are:

  • If your furnace isn’t turning on when you adjust the thermostat, it could be due to a malfunctioning ignitor. The ignitor may hinder ignition, preventing the furnace from operating correctly. 
  • In case of a failed ignitor, the heating process gets compromised. This leads to insufficient warm air circulation, resulting in a noticeable lack of airflow from your heating system. 
  • Seeing unusual or erratic flames, such as flickering or irregular patterns, indicates an ignitor issue affecting combustion. 
  • A malfunctioning ignitor can cause your furnace to cycle frequently, leading to an inefficient and unreliable heating system. This results in the system struggling to maintain a consistent temperature. 
  • If your furnace repeatedly trips the circuit breaker, it could be due to ignitor problems, causing electrical issues that disrupt the furnace’s operation. 
  • A clicking sound without the furnace’s start indicates ignition failure, often linked to an ignitor issue. This prevents the heating process from initiating.

A direct ignition furnace uses electronic ignition to start the burner without a pilot light. It only consumes fuel when heating is required, making it energy-efficient and cost-effective. It eliminates gas wastage and increases safety by reducing the risk of gas leaks or accidental combustion. The ignition is controlled by a board, ensuring reliable ignition every time.

Implementing essential gas furnace repair strategies is crucial to keep your heating system running efficiently. Identify the issue by recognizing common symptoms such as faulty thermostats, clogged filters, or malfunctioning pilot lights. Once the problem is identified, apply appropriate repair strategies. Regular maintenance, like cleaning or replacing air filters, is crucial for proper airflow and preventing system breakdowns.

Regular maintenance and ensuring proper pilot light ignition can solve most furnace issues. Seek professional help for complex situations like a malfunctioning ignition or a damaged heat exchanger. Gas furnace repair can efficiently address problems, extend the furnace’s lifespan, and ensure optimal performance.


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